huschi.net

GETITIMER(3P)              POSIX Programmer's Manual             GETITIMER(3P)

PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
       implementation of this interface may differ (consult the  corresponding
       Linux  manual page for details of Linux behavior), or the interface may
       not be implemented on Linux.
NAME
       getitimer, setitimer - get and set value of interval timer
SYNOPSIS
       #include <sys/time.h>
       int getitimer(int which, struct itimerval *value);
       int setitimer(int which, const struct itimerval *restrict value,
              struct itimerval *restrict ovalue);

DESCRIPTION
       The getitimer() function shall store the current  value  of  the  timer
       specified  by  which  into  the  structure  pointed  to  by  value. The
       setitimer() function shall set the timer  specified  by  which  to  the
       value  specified in the structure pointed to by value, and if ovalue is
       not a null pointer, store the previous value of the timer in the struc-
       ture pointed to by ovalue.
       A  timer  value  is  defined  by  the itimerval structure, specified in
       <sys/time.h>. If it_value is non-zero, it shall indicate  the  time  to
       the next timer expiration. If it_interval is non-zero, it shall specify
       a value to be used in reloading it_value when the timer  expires.  Set-
       ting  it_value  to  0 shall disable a timer, regardless of the value of
       it_interval. Setting it_interval to 0 shall disable a timer  after  its
       next expiration (assuming it_value is non-zero).
       Implementations  may place limitations on the granularity of timer val-
       ues. For each interval timer, if the requested timer value  requires  a
       finer  granularity  than  the implementation supports, the actual timer
       value shall be rounded up to the next supported value.
       An XSI-conforming implementation provides each process  with  at  least
       three interval timers, which are indicated by the which argument:
       ITIMER_REAL
              Decrements in real time. A SIGALRM signal is delivered when this
              timer expires.
       ITIMER_VIRTUAL
              Decrements in process  virtual  time.  It  runs  only  when  the
              process  is  executing.  A SIGVTALRM signal is delivered when it
              expires.
       ITIMER_PROF
              Decrements both in process virtual time and when the  system  is
              running  on  behalf of the process. It is designed to be used by
              interpreters in statistically profiling the execution of  inter-
              preted  programs.  Each  time the ITIMER_PROF timer expires, the
              SIGPROF signal is delivered.

       The interaction between setitimer() and any  of  alarm(),  sleep(),  or
       usleep() is unspecified.
RETURN VALUE
       Upon  successful completion, getitimer() or setitimer() shall return 0;
       otherwise, -1 shall be returned and errno set to indicate the error.
ERRORS
       The setitimer() function shall fail if:
       EINVAL The value argument is not in canonical form. (In canonical form,
              the  number  of microseconds is a non-negative integer less than
              1000000 and the number of seconds is a non-negative integer.)

       The getitimer() and setitimer() functions may fail if:
       EINVAL The which argument is not recognized.

       The following sections are informative.
EXAMPLES
       None.
APPLICATION USAGE
       None.
RATIONALE
       None.
FUTURE DIRECTIONS
       None.
SEE ALSO
       alarm(), sleep(), timer_getoverrun(), ualarm(), usleep(), the Base Def-
       initions volume of IEEE Std 1003.1-2001, <signal.h>, <sys/time.h>
COPYRIGHT
       Portions  of  this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
       Specifications Issue 6, Copyright (C) 2001-2003  by  the  Institute  of
       Electrical  and  Electronics  Engineers, Inc and The Open Group. In the
       event of any discrepancy between this version and the original IEEE and
       The  Open Group Standard, the original IEEE and The Open Group Standard
       is the referee document. The original Standard can be  obtained  online
       at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group                  2003                        GETITIMER(3P)